Improvement in proportional scales for the construction of toothed gear



LToh/1 mu/er, am?. 1. 50a/e for Cog W/Zfe/s, Rar/is, Za

1 l Q 0 Q 7 PATE-NW10 FEB 21 1871 www [muni-Illu martire Pill witnesses, file/m 62W.

lirici can JOHN W'ALtrllK, Uli PHILADELPHIA, PENNSYLVANIA.

'Lea-ers .Patent No. 112.091, atedrebruary 21, 1871.

'rhs Schedule referred to ln-theoe Letters Patent and making part of the same.

l', JOHN WALKER, a subject of the (,lueenof Great: Britain and Ireland, at present residing in Philadelphia, county of Philadelphia, Stateof Pennsylvania, have invented a Scale for Cog-Xlllleels, Racks, Sie., ot' which the following is aspecitication.

Nature and Object of the Intention,

My invention consistsof a scale, fully explained hereafter, for readily and quickly determining the size andsha-pe of the teeth ol' all kinds of cog-wheels, racks, worms, v&e., without any ot' the tedious calculations which are usually required in this class ot' work.

`the same diameter', gearedtogether and'having teeth designed'froni the scale; l Figure 4, alview ot a portion oi' two cog-wheels-ot .different diameters; and

Figure 5, a diagram showing the method otA using the scale in designinr the teeth of' racks'andit' worms for wor1n-wheelsh'cncrltl Description..

lhc cog-teeth represented in sheet 2.0i' the drawingare ,of the kind which jtis designed to produce b'y the scale, they beiner of what is commonly known as the lgee pattern;v or, in othei` words, their working edges are formed on two curves or parts of circles, au outwardly-ionnding'enrx'e,u1', fig. 2, from the point of the tooth to the pitchline, and an inwardlyyrounding the rootof the tooth. Wheels having teeth ot' this pattern worlttogethcr with little friction, and have several other advantages which will be more particularly referred to hereafter.`

By means of the scale the most advantageous curves l'oikthe working edges ot' any tooth ofa given pitch, as wellras the length of the tooth, and other data which have usually been .obtained by tedious calculations, can' be readily determined.

The complete scale is illustrated in tig. l', andgeonsists offonr main parts,eaeh ofwhie-horms in itself a lle for determining certain points.v

'T le portion A of the scale is ot'a triangular'- shape,.- and consists of lines a c' of, 85e., converging tewatd single point, and Viutersoeted by parallel lines bionwhich are marked the 'pitches, li'mfionc-'quarter gif an inch to six inc-hes.l f

The portion B of 'the .scale is directly opposite and similar .to the portion A, and consists of converging lines c cl c2, 8:0., whichcross the parallel pitch-lines l). The third portion C of the-scale., is for determining the width of the roots-of the teeth, and is made up of' parallel `lines d, upon whicharemarked numbers from 0 to 200, indicating nn'mbers of teeth in different wheels, and ot' converging lines e, crossing the lines-l,and curved-at the ends where they most nearly approach each other. The lines e are marked with numbers from() to (i, indicating' diierent pitches. ,The fourth division D of the scale is for determinimar the proper widthoi` the'points of teeth, and is precisely similar tothe above-described portion C, except that it is narrowerthroughout. l

In order to explain the method of using thescale,

wheel of eleven sindonehalf inches'adius, and to have'twenty'onr teethof three-inch pitch, is\.to be determined` .l V

The mdius line jf and curved pitch-line y, on the radius of eleven'and' one-.half inches, are Ifirst drawn as shown i'n iig. 2. Then, with a pair of compasses, thedistanco on theldivision A of the scale, fi'ourthe line a 'to the line aff, on the pitehfline 3, is taken and transi'brred tothe drawing to determine the position oi' the curved root line 11, which isdrawn as shown.

y The curved lined for thejpoints of the teeth isnext determined and drawn in a similar manner by meas.- nringthe distance on the scale between the lines a? and u on the same pitch-linc'.

The width ot' the tooth at the root is next ascertained by measuring with the Compasses, on the di- 1Vision G of the scalo, the distance ou the line 24, (the number of teeth oi' proposed wheel,) between the pitch lines 0 and 3. p

This measurement. is laidolf on y,each side ofthe ra dius fupon the root line h, thepoints being marked 7' in thcdrawiig.

The width ot' the tooth at the,poi'nt isvascertained midis laid to the points 7.: Lupon the line i.

For the width ofthe tooth at th'egiitch line a" measurement istaken on the division B ofthe le, 'b-

is -laidoii' on points l Z.

4me-length of the' tooth andthe .points j, Ivy-and l, maxjtingitsywidth; havingfbeen thus ascertained, `it only remains 'to ,detelinine'the fjii'opercu'rves for"l the lines Q: and :1c,.th,e|-radin'sesfor ,Strikingavhic are vto v hefnrid 'ppenthe'ldivisionA of the scale. radins for ,the;fline-`a:.-is fou'udr by,-meainr'ingP eithers'nlc ot' the ,radins 'to:.obtainthe det it be. supposed .that the', shape ofthe teethof a tween thc lines lcandc?, -on ,the pitch 1ine13, and thisl upon the saine pitch-line, the distance between the lines a and fff". v

These measurements are transferred to the drawing, andthe curves .fr and fc' drawn, the proper centers being found, if thought necessary, bylneans "of the radinses y y y, &c., indicated in dotted lines.

The proper curve for the fillets @at the root of the tooth, can he determined by measuring; thedistance between the lines a and al on the pitch line 3 of the division A, which will give the radins.

' In calculating Ifor teeth of adilierent pitch 'from that above deseribed,`a pitch of two inches, for `instance, all measurements would'berniade npon the pitch-line 2, in the different divisions of the scale, or

upon any' other-lwaarneming `t0 the pitch determined upon.

Fig. 3 illustrates a portion oftwo cog-wheels ofthe same diameter geared together, and having teeth designed from the scale in the manner above described; and fig. 4 illustrates poi-tiens of tiwfjo'cog-wlieels't' different diameters, the teeth ofwhielrare also designed iorn the'scale. l

vIn 5 a rack-tooth is shown. This .is designed from the scaledn the same manner as the wheel-teeth, except that upon the divisions `,C and D yof the scale all measu'rtnnents are 'madcfiipon one'line,.as"imli cated, there being no limit tofthenuniber otfteeth.-

wheels are determined ingzthe. saine manner ast'or racks, and for internal cog-wheels all the measure'- mentsupon the divisions U and D are likewise 1 upon a single line, as shown.

In ascertaining the measurements for the teeth oil nadev ,91, Snel, Z and e, the `whole same pitch will be interchangeable; for instance, a'y pinion of twelve teeth will Werl; into another' pinion of the same number of teeth, or with a wheel havin g any. greater number` of teeth, or any `eog-whcel or pinion will gear properly with a racle or internal eogl wheel of the saine pitch.

No'templets will in any ease` behreg'piired, and in preparingl patterns for wheclsit will only be necessaryA to construct one'tooth upon thedrawing-hoard.

- hC'la'finL The scale, consisting of the divisions A, 13,0, and D, theirletters and numerals,v 'and lines c a), Src., b, c being constructed and ar ranged as set forth.,.

lntestiinony whcreofl' have signed niylna-me Ate this specification in the presence ot'two subscribing' witnesses. t

JOHN XVALKER, Witnesses YVM. A. STEEL, JN0'. 1%. HARDING. 

